The present invention relates to a system for monitoring the vital signs of heavy machines, and specifically relates to a system for monitoring the level of indicator materials in the lubricant to pinpoint the location of malfunctioning machine components.
The maintenance of heavy machinery has traditionally been an expensive and time consuming operation. Modern production schedules often require these machines to be in operation for extended periods of time, and often continuous operation is required. Consequently, preventive machine maintenance has evolved from a process practiced only by the more progressive machine operators, to a requirement of all profit minded operators.
An example of how preventive machine maintenance can affect the economics of machine operation is found in the process machinery industry, which provides heavy duty machines such as rock crushers used in mining and road building.
Bearing failure is a major cause of rock crusher breakdown, and is also a major source of maintenance expenditures in this industry. It normally takes from 50 to 100 man hours to dismantle a rock crusher in order to change worn bearings, each of which may be very costly. In an effort to minimize maintenance costs due to malfunctioning bearings, manufacturers have developed methods of monitoring the bearing condition to predict and minimize machine breakdowns due to bearing failure.
There are several indicia of machine condition which can be monitored to predict and prevent bearing failure. The following examples will be provided in the context of a rock crusher, however, the same principles can be used for most types of production machinery. For machines having an internal bearing lubrication system, means have been developed to measure lubricant temperature in various parts of the machine to detect differences in lubricant temperature which indicate excessive friction. If the temperature differential exceeds a pre-set threshold, some kind of alarm signal will be triggered. Similarly, lubricating or hydraulic oil pressure can be monitored to detect machine malfunctions by activating an alarm if oil pressure falls below a pre-set figure. Machine vital signs can further be monitored by the use of a sensing device which measures the revolutions per minute of various moving parts to ensure that shaft speed is maintained within desired limits. A slow moving shaft may indicate excess friction caused by a worn bearing. Sensing devices have also been developed to measure electric motor power draw and the level of lubrication oil in a holding tank. These sensing systems can be either manually or automatically monitored.
A major drawback of the above-mentioned sensing systems is that although machine failure can be detected and prevented, it has previously been impossible to ascertain the exact location of the malfunctioning component. Thus, when any or all of the above-mentioned sensing devices become activated, normally large portions of the affected machine must be dismantled to discover and repair or replace malfunctioning machine components.
Consequently, there is a definite need for a machine maintenance system which is capable of both monitoring machine condition and pinpointing the exact location of the malfunctioning element. This problem is especially critical in the area of machine bearing maintenance.
It is therefore a major objective of the present invention to provide a machine condition diagnostic system which is capable of monitoring the bearing lubricant over extended periods of tme to detect instances of excessive component wear, as well as being able to pinpoint the exact location of an existing or pending malfunction so that maintenance can be accomplished in much shorter periods of time while incurrin9 lower costs.